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Understanding heredity

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Presentation on theme: "Understanding heredity"— Presentation transcript:

1 Understanding heredity
Part 2

2 mutations

3 Mutations Genes code for proteins
Mistakes in genetic code cause mistakes in the protein Mutations are mistakes in genetic code A point mutation involves one nitrogen base in a codon Some point mutations cause no difference in protein produced Others point mutations can cause a noticeable or serious effect

4 Mutations, cont. Types of Point Mutations:
Substitution – one nucleotide is changed to another Example: CAT GCA CAG GCA Insertion – one nucleotide is inserted into a sequence Example: CAT GCA CAG TGC A Deletion – one nucleotide is deleted from a sequence Example: CAT GCA CAG CA

5 Mutations, cont. Substitutions usually affect only one amino acid
Insertions or deletions can result in a frameshift mutation – they shift the “reading frame” of the bases This can change every amino acid that follows the point of mutation

6 Mutations, cont. Chromosomal mutations – involve changes in the number or structure of chromosomes Some may change the locations of genes on chromosomes Others may change the number of copies of a gene made

7 Mutations, cont. Types of Chromosomal Mutations:
Deletion – an entire gene is deleted Duplication – an extra copy of the gene is added Inversion – a segment of the chromosome is flipped over Translocation – a portion of a chromosome breaks off and reattaches to another chromosome

8 Mutations,cont. Many mutations are neutral – they have little/no effect on the expression of genes or the function of proteins for which they code Some mutations can result in the production of defective proteins that disrupt normal biological activities Harmful disruptions cause many genetic disorders Beneficial disruptions can be the source of genetic variation that allows certain members of a species to be more successful in a changing environment

9 Mutations, cont. Polyploidy – condition in which an organism has an extra set of chromosomes Occurs during meiosis when the chromosomes fail to separate Triploid- 3N Tetraploid- 4N In animals: polyploidy is deadly In plants: benefits – larger, stronger; source of seedless fruits drawbacks – cannot be fertilized; have to purchase seed to make more plants

10 Genetic disorders

11 Genetic Disorders Genetic disorder – disease caused by an abnormality in the organism’s DNA Single-gene disorders are inherited in Mendelian patterns: Autosomal recessive disorders Autosomal dominant disorders Sex-linked patterns

12 Genetic Disorders, cont.
Autosomal Recessive Disorders: Most human genetic disorders are caused by recessive alleles on autosomes This means the individual must inherit two copies of the recessive allele Examples: Sickle-cell Disease – red blood cells develop a rigid sickle shape; blood cells clot and cause oxygen loss to body cells Cystic Fibrosis – thick mucus secretions in lung, pancreas, liver and intestines Tay-Sachs Disease – progressive degeneration of all nerve cells starting about 6 months old with death by 4

13 Genetic Disorders, cont.
2. Autosomal Dominant Disorders: Less common than recessive because they are often lethal In most cases, individuals with disorder live long enough to reproduce Keeps allele in population Examples: Huntington’s Disease & Marfan Syndrome

14 Huntington’s Disease –
degeneration of nerves affects muscle coordination causes mental and emotional decline starts in mid-life most common cause of death is pneumonia; second most common is suicide

15 Marfan Syndrome - affects proper growth of connective tissue individuals are unusually tall, with long & thin limbs/toes/fingers disruption of proper heart function is most serious complication

16 Genetic Disorders, cont.
Sex-Linked Patterns Females: XX Males: XY Y chromosome contains the gene, SRY, that codes for development of the testes If testes form, other genes guide production of testosterone and fetus develops into a male If Y chromosome is absent or SRY gene does not function correctly, fetus develops into a female

17 Genetic Disorders, cont.
Genes located on sex chromosomes are called sex-linked genes Many genes are found on the X chromosome, but not the Y chromosome Because there is not an alternate allele on the Y chromosome, the allele on the X is the one expressed Sex-linked = X-linked Examples of X-linked disorders: Color blindness – inability to see some, or all, colors in the normal way Hemophilia – blood disorder in which blood does not clot properly (have low to no clotting factor in blood)

18 Pedigree Chart – Queen Victoria of England (died 1901)
Died: 1945, no children

19 biotechnology

20 Biotechnology Biotechnology – use of living organisms to improve the quality of human life

21 Biotechnology, cont. Bacteria are the most commonly used organisms in biotechnology This is because their DNA is not surrounded by a nucleus and is easier to manipulate Also, manipulated bacteria reproduce rapidly Insulin, produced by E.coli bacteria, is the first protein commercially manufactured using this method

22 Biotechnology, cont. Human DNA is 99.9% identical
The .1% difference is displayed in fingerprints, inherited health conditions and appearance Gel electrophoresis is a process used by scientists to isolate and study specific proteins This increases our understanding about how proteins work and how we can utilize them to a better quality of life

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